1. Field of the Invention
The present invention relates to a coolant passage apparatus used suitably for a cooling device which cools an internal combustion engine (hereinafter also referred to as engine) by circulating a coolant between a fluid passage formed in the internal combustion engine and a radiator.
2. Description of the Related Art
In this type of engine cooling device, it is arranged that not only an engine is cooled by circulating a coolant between a fluid passage formed in the internal combustion engine and a radiator but also the coolant is supplied to a heater circulation channel provided with a heater core for heating. Furthermore, in these days it is proposed that the coolant from the engine is also used for an ATF (Automatic Transmission Fluid) warmer or an EGR (Exhaust Gas Recirculation) cooler.
Therefore, as described above, in order that the coolant is circulated in or supplied to each part, it becomes necessary to use a branch pipe separately and connect it to piping. Thus, there arises a problem that the piping in an engine room becomes complicated and worsens engine maintenance.
Then, in order to simplify connection of the pipes described above, a coolant passage apparatus is disclosed in prior art shown below in which the piping is directly attached to a coolant discharging outlet of the engine, a thermo valve is accommodated in the piping, and connection parts of the pipes are collected.
Incidentally, the coolant passage apparatus disclosed in Japanese Patent Publication No. H4-16610 has a complicated structure including, for example, a collecting pipe for receiving and collecting a coolant by directly connecting a pair of respective banks of a V-engine, a by-pass passage, an outlet for supplying the coolant to a radiator, an inlet for receiving the coolant from the radiator, a piping connection part for a water pump, etc.
In such a coolant passage apparatus, the whole apparatus is molded from a metal material, so that the molding process is not so easy. Thus, there arises a problem in that the molding process adds costs and increases its weight.
Then, the applicants have filed a patent application, Japanese Patent Application No. 2009-41771 entitled “Coolant Passage Apparatus” in which the whole coolant passage apparatus is molded from a synthetic resin so as to reduce its weight and costs taking advantage of the ease of resin mold.
According to our earlier application filed by the applicants entitled “Coolant Passage Apparatus”, it is possible to obtain sufficient machining accuracy with respect to a required portion, the whole apparatus can absorb and disperse stress applied to the apparatus, and it becomes possible to effectively cope with the stress caused by thermal expansion of the engine and an offset of a joint caused by a difference in thermal expansion coefficient between the engine and the above-mentioned equipment.
FIGS. 9 and 10 show an example of the coolant passage apparatus of the patent application filed by the applicants previously. In addition, FIG. 9 is a perspective view showing the apparatus viewed from the rear, which is separated into first and second bodies (situation before both are joined together) and FIG. 10 is a front view showing the coolant passage apparatus viewed from the front whose bodies are joined together.
In the coolant passage apparatus 10, shown in FIGS. 9 and 10, of the earlier application, a pair of coolant receiving pipes 11 and 12 which respectively receive the coolant discharged from the right and left engine heads in the V-engine are provided on the first body 31 side, and a central passage 19 which collects the coolant, a communicating tube 21 which is towards the radiator through the above-mentioned central passage 19, etc. are provided on the second body 32 side. The first body 31 and second body 32 molded from a resin are joined together by a welding means, for example, to form the coolant passage apparatus 10.
Incidentally, in the coolant passage apparatus 10 proposed previously, the pair of coolant receiving pipes 11 and 12 are arranged to communicate with the riser pipes 17 and 18 which rise perpendicularly and communicate with the above-mentioned central passage 19 which is formed horizontally through these riser pipes 17 and 18.
In other words, assuming that a line passing through the center of the above-mentioned central passage 19 in the passage apparatus 10 is (indicated by) A which is horizontal, lines B passing through the centers of the above-mentioned riser pipes 17 and 18 rise at right angles to the above-mentioned line A to be perpendicular. Further, lines C passing through the centers of the pair of coolant receiving pipes 11 and 12 are arranged at right angles to the above-mentioned lines B to be horizontal.
Therefore, according to the coolant passage apparatus 10 having the above-described structure, the coolant flows out towards the communicating tube 21 which is towards the radiator, being turned at substantially right angles in order of lines C→B→A. Thus, the coolant which passes through (the inside of) the apparatus 10 is a complicated flow along a plurality of right-angled bends. For this reason, resistance takes place in the flow of the coolant, which affects a flow rate of the coolant, thus there arises a problem of affecting the cooling capacity of the whole engine.
Further, in the coolant passage apparatus 10 proposed previously, since a channel from the pair of coolant receiving pipes 11 and 12 to the communicating tube 21 which is towards the radiator is arranged to be bent substantially at right angles continuously as described above, the whole apparatus 10 becomes larger naturally. For this reason, it is often the case that stress is generated by the difference in thermal expansion coefficient between the engine and the above-mentioned apparatus 10, and another device for absorbing this is also needed.
Furthermore, in the coolant passage apparatus 10 having the above-described structure, the total length around the junction portion for joining the first body 31 to the second body 32 which are molded from a resin becomes long, so that particular device is also required in order to secure the reliability against the leakage at the junction portion, and there is room for further improvement.